A Ultra Low-Voltage, Low-Power RF Voltage Controlled Oscillator And Its Prescaler

The explosive growth in wireless communications has driven universities and companies to produce wireless transceivers at low-cost, low-power, and compact size. The VCO and the prescaler are the critical parts of the PLL frequency synthesizer, they determine some of the PLL's important features, e.g. tuning range, phase noise, power consumption.The line-width of CMOS technologies is projected to keep scaling deeper into nanoscale dimensions for the next two decades. This will increase the functionality density, the intrinsic speed of the devices and thus the signal processing capability of the circuits. However, in order to maintain reliability, to avoid breakdown, to avoid thermal problems and to reduce power density, the maximum supply voltage has to be scaled down appropriately. But the transistor's threshold voltage is not reduced as aggressively. The low power supply voltages and the relatively large device threshold voltages are an obstacle to high performance analog circuit design. At supply voltages below 1 V, the design of analog circuits becomes very challenging since the traditional circuit techniques do not have sufficient voltage headroom.This thesis aims at designing two groups of VCOs and prescalers for low voltage application, which work in the 2.4 GHz,6 GHz environments respectively. The main contents and innovative points of this dissertation are list below.Firstly, it researched the basic components of the RF circuit, which include RF MOSFET. integrated inductor, integrated varactor, and their applications. It summarized the structure classification, the working principle and the design guideline of the LC VCO and its prescaler. It paid special attention to the design method in the low voltage environment.Secondly, two VCOs under 0.5 V supply voltage are implemented in SMIC 65 nm 1P8M CMOS process. The measurement results show that, the 2.4 GHz VCO achieves 2.419～2.116 GHz tuning range with the power consumption of 2.5 mW; this VCO is used to constitute a PLL. the phase noise is-118.33～-122.34 dBc/Hz@1MHz, the FOM is better than-186 dB; the 6 GHz VCO achieves 6.209～5.666 GHz tuning range with the power consumption of 3 mW. and the phase noise is-108.74～-111.17dBc/Hz@1MHz, the FOM is-183 dB.Finally, two prescalers under 0.8 V supply voltage are implemented in SMIC 65 nm 1P8M CMOS process. The measurement results show that, both can function smoothly in the tuning range of their respective VCOs. The 2.4 GHz prescaler achieves the dual modulus division by 256/258 and consumes 0.58 mW power; the 6 GHz prescaler achieves the dual modulus division by 32/33 and consumes 0.3 mW power.